Update of the major results from the GALLEX Cr-neutrino source experiment

This report provides an update about the major results of the GALLEX Cr-neutrino source experiment since November 8, 1994 and reports results of individual measurements of source activity. New data does not change the main conclusion from the November 8, 1994 data: Unknown systematical errors in GALLEX can at the most be of order 10%. 3 refs., 1 fig., 2 tabs

Maximum likelihood analysis of the first KamLAND results

A maximum likelihood approach has been used to analize the first results from KamLAND emphasizing the application of this method for low statistics samples. The goodness of fit has been determined exploiting a simple Monte Carlo approach in order to test two different null hytpotheses. It turns out that with the present statistics the neutrino oscillation hypothesis has a significance of about 90% (the best-fit for the oscillation parameters from KamLAND are found to be: $\delta m_{12}^2 \sim 7.1 \times 10^{-5}$ eV$^2$ and $\sin^2 \theta_{12} = 0.424/0.576$), while the no-oscillation hypothesis of about 50%. Through the likelihood ratio the hypothesis of no disappearence is rejected at about 99.9% C.L. with the present data from the positron spectrum. A comparison with other analyses is presented.Comment: 14 pages, 5 figure

The Problem of Large Leptonic Mixing

Unlike in the quark sector where simple $S_3$ permutation symmetries can generate the general features of quark masses and mixings, we find it impossible (under conditions of hierarchy for the charged leptons and without considering the see-saw mechanism or a more elaborate extension of the SM) to guarantee large leptonic mixing angles with any general symmetry or transformation of only known particles. If such symmetries exist, they must be realized in more extended scenarios.Comment: RevTeX, 4 pages, no figure

Atmospheric neutrino oscillations in three-flavor neutrinos

We analyzed the atmospheric neutrino experiments of SuperKamiokande including zenith angle dependence's using the three-flavor neutrino framework with the hierarchy m^2_1 \approx m^2_2<<m^2_3. Taking into account the terrestrial, solar neutrino experimental data and the atmospheric neutrino experiments including the sub-GeV and multi-GeV data in SuperKamiokande, large angle solution in the solar neutrino experiments is favored and the range of the mass parameter Deltam^2_{23} is restricted between 0.08eV^2 - 2eV^2. Allowed regions of mixing parameters are (theta_{13}<4degree, 27degree<theta_{23}< 32degree) for Delta m_{23}^2=1eV^2 and (theta_{13}<3degree, 28degree<theta_{23} <33degree) for Deltam_{23}^2=0.1 eV^2.Comment: 21 pages, LaTe

Future ντ\nu_\tau Oscillation Experiments and Present Data

Our goal in this paper is to examine the discovery potential of laboratory experiments searching for the oscillation $\nu_\mu(\nu_e) \rightarrow \nu_\tau$, in the light of recent data on solar and atmospheric neutrino experiments, which we analyse together with the most restrictive results from laboratory experiments on neutrino oscillations. In order to explain simultaneously $all$ present results we use a four-neutrino framework, with an additional sterile neutrino. Our predictions are rather pessimistic for the upcoming experiments NOMAD and CHORUS, which, we find, are able to explore only a small area of the oscillation parameter space. On the other hand, the discovery potential of future experiments is much larger. We consider three examples. E803, which is approved to operate in the future Fermilab main injector beam line, MINOS, a proposed long-baseline experiment also using the Fermilab beam, and NAUSICAA, an improved detector which improves by an order of magnitude the performance of CHORUS/NOMAD and can be operated either at CERN or at Fermilab beams. We find that those experiments can cover a very substantial fraction of the oscillation parameter space, having thus a very good chance of discovering $both$ $\nu_\mu \rightarrow \nu_\tau$ and $\nu_e \rightarrow \nu_\tau$ oscillation modes.Comment: Latex file using ReVTeX and epsifig.sty. 40 Pages. Revised version includes new references and changed Fig.